The present invention is a micro-electrical-mechanical system (MEMS) switch.
Micro-electrical-mechanical system (MEMS) switches are well known and disclosed, for example, in the following U.S. Patents.
These switches are typically configured as a cantilever or suspended mass structure and have a switch contact that moves in a generally perpendicular direction with respect to the plane of the substrate on which the device is fabricated. Unfortunately, the frequency response of these xe2x80x9cverticallyxe2x80x9d actuated switches is insufficient for certain applications. The polysilicon-to-polysilicon electrical contacts of these switches often exhibit relatively high resistance due to oxidation of the opposing silicon surfaces.
Still other MEMS actuators include electrostatic combs having a plurality of electrodes. For example, U.S. Pat. No. 6,133,670 discloses an electrostatic comb actuator having a fixed comb electrode and a moving comb electrode supported by a spring. Both the fixed and moving comb electrodes have a plurality of elongated fingers arranged generally parallel to one another at spaced-apart positions. In a rest position with no electric actuation voltage, the fingers of the fixed comb electrode are partially meshed (i.e. interdigitated to a predetermined extent) with the fingers of the moving comb electrode. In response to an electric actuation voltage, forces move the moving comb towards the fixed comb in a direction parallel with a longitudinal axis of the electrode fingers against the restoring force of the spring. MEMS devices of this type require a relatively high actuation voltage to operate the moving electrodes.
Therefore, there remains a continuing need for improved MEMS switches. In particular, there is a need for relatively high-frequency, low-noise MEMS switches. Switches of these types that have a relatively low actuation voltage would be especially desirable.
The present invention is a MEMS switch that can be configured for high-frequency, low actuation voltage, low noise and low contact resistance operation. One embodiment of the invention includes a substrate defining a plane, first and second switch contacts and a contact shuttle that is movable in a linear path parallel to the plane of the substrate between first and second switch state positions with respect to the switch contacts. A spring biases the contact shuttle to the first switch state position. A plurality of moving electrodes are coupled to the contact shuttle and have generally planar major surfaces perpendicular to the plane of the substrate. A plurality of fixed electrodes, each located interleaved with and adjacent to one of the moving electrodes, have generally planar major surfaces perpendicular to the plane of the substrate. In response to the application of an electric actuation voltage, electrostatic forces develop between the moving and fixed electrodes causing the moving electrodes to move along an axis parallel to the plane of the substrate and perpendicular to the planar major surfaces of the electrodes, thereby forcing the contact shuttle to move to the second switch state position.
Another embodiment of the switch includes a substrate and a contact shuttle movable with respect to the substrate between switch state positions. A plurality of moving electrodes are coupled to the contact shuttle at spaced-apart locations and have generally planar major surfaces facing each other to form a comb structure. A plurality of fixed electrodes are coupled to the substrate at spaced-apart locations and have generally planar major surfaces facing each other to form a comb structure. The fixed electrode comb structure is interleaved with the moving electrode comb structure. In response to the application of an electric actuation voltage, electrostatic forces develop between the moving and fixed electrodes causing the major surfaces of the moving electrodes to move with respect to the major surfaces of the fixed electrodes, thereby forcing the contact shuttle to move between the switch state positions along a longitudinal axis parallel to the substrate and perpendicular to the planar major surfaces of the electrodes.
Yet another embodiment of the switch includes a driven member and a contact shuttle connected to the driven member. The contact shuttle is movable between switch state positions with respect to the switch contacts. An oxide insulator electrically isolates the contact shuttle and the driven member.